🧬 Biology · Topic 2 of 10
Start with the study notes on Food: Sources & Components (definitions, examples and a quick revision), then work through 60 practice questions, each with the correct answer and a clear explanation of why it is right. When you are ready, take this topic as an interactive quiz to test yourself.
Topic overview
All our food comes from plants or animals.
Remember: A potato is a stem, not a root. Its “eyes” are buds, and roots never have buds.
Example: Bees make honey from the nectar of flowers.
Food contains nutrients (carbohydrates, proteins, fats, vitamins and minerals), along with water and roughage. Each has its own job.
Energy-giving: carbohydrates, fats · Body-building: proteins · Protective: vitamins, minerals
Carbohydrates are the body's main source of energy. They are starch and sugars.
Examples:
Proteins are body-building foods. They help us grow and repair damaged parts.
Example: Pulses, soybean, milk, paneer, eggs, fish and meat.
Fats give more energy than the same amount of carbohydrates, and are stored in the body for later use.
Example: Butter, ghee, oil, groundnuts and nuts.
Vitamins and minerals are protective foods. They are needed in small amounts, but they keep the body healthy and protect it from disease.
A balanced diet contains all the nutrients, plus water and roughage, in the right amounts. It need not be expensive: pulses, seasonal vegetables, millets and sprouts are cheap and nutritious.
Example: Chapati, dal, a vegetable, curd and a fruit make a balanced meal.
A deficiency disease is caused by lacking a nutrient for a long time:
Remember: Wash vegetables before cutting them, and don't overcook them. Vitamins B and C dissolve in water and are destroyed by heat.
| Misconception | Correct understanding |
|---|---|
| A potato is a root. | It is an underground stem; its eyes are buds. |
| Vitamins give us energy. | Vitamins protect and regulate the body; carbohydrates and fats give energy. |
| Roughage is useless because it isn't digested. | It prevents constipation and keeps digestion healthy. |
| A healthy diet must be expensive. | Cheap local foods like pulses, millets and sprouts are very nutritious. |
| More of one good food is enough. | No single food has everything; we need a balanced diet. |
Which part of the plant is a carrot?
The root.
What is the main energy-giving nutrient?
Carbohydrates.
Name two good sources of protein.
Pulses and eggs (also milk, fish and meat).
Which vitamin can our skin make in sunlight?
Vitamin D.
Lack of which vitamin causes scurvy?
Vitamin C.
Which mineral prevents anaemia?
Iron.
How do you test a food for starch?
Add iodine solution; a blue-black colour shows starch.
Why should vegetables be washed before cutting?
Water-soluble vitamins would wash out of the cut surfaces.
Key takeaway: Carbohydrates and fats give energy, proteins build the body, vitamins and minerals protect it, and a balanced diet gives you all of them.
Notes written by Velnov for Class 6–8 students, following the topics of the NCERT science syllabus.
Q1. easy
The two main sources of food are:
Answer: A — Plants and animals
All our food comes from plants (grains, fruits, vegetables, pulses) or from animals (milk, eggs, meat, honey). Even animal food ultimately depends on plants.
Q2. easy
Animals that eat only PLANTS are called:
Answer: A — Herbivores
Cows, goats, deer and elephants are herbivores. They usually have flat grinding teeth suited to chewing plant material.
Q3. medium
Animals that eat only OTHER ANIMALS are called:
Answer: A — Carnivores
Lions, tigers and snakes are carnivores. They have sharp pointed teeth and claws for catching and tearing flesh.
Q4. medium
Animals that eat BOTH plants and animals are called:
Answer: A — Omnivores
Human beings, crows, bears and dogs are omnivores, eating both plant and animal food. This flexible diet helps them survive in many habitats.
Q6. medium
Which part of a plant do we eat when we eat a CARROT?
Answer: A — The root
Carrot, radish, beetroot and sweet potato are all roots that store food. Potato, in contrast, is an underground stem.
Q8. medium
Which of these do we eat as a FLOWER?
Answer: A — Cauliflower
Cauliflower and broccoli are flower clusters. Cabbage and spinach are leaves, and carrot is a root.
Q10. medium
The main components of food are:
Answer: A — Carbohydrates, proteins, fats, vitamins, minerals, water and dietary fibre
These seven components are called nutrients (except water and roughage, which are equally essential). Each has its own role in keeping the body healthy.
Q11. medium
Which nutrient is the body's MAIN source of energy?
Answer: A — Carbohydrates
Carbohydrates - starch and sugars - are broken down to glucose, which supplies most of the energy our cells need for daily activity.
Q13. medium
Which test is used to detect STARCH in food?
Food + iodine solution → blue-black colour = starch presentAnswer: A — Iodine test - the food turns blue-black
A drop of dilute iodine solution on a food containing starch produces a distinctive blue-black colour. Rice, potato and bread all give a positive result.
Q15. medium
The test for FAT involves rubbing the food on paper and looking for:
Answer: A — An oily translucent patch that lets light through
Fat leaves a greasy patch on paper that remains translucent even after the paper dries - unlike a water mark, which disappears.
Q17. medium
Which of these is a rich source of PROTEIN?
Answer: A — Pulses, milk, eggs, fish and meat
Pulses, soybean, gram, milk, paneer, eggs, fish and meat are protein-rich. Rice and potato give carbohydrates, and butter and ghee give fats.
Q19. medium
Which of these foods is rich in FAT?
Answer: A — Butter, ghee, groundnut and oil
Butter, ghee, cooking oils, nuts, groundnuts and cheese are fat-rich. Nuts and seeds also give useful proteins and minerals.
Q21. medium
Vitamins and minerals are called PROTECTIVE foods because they:
Answer: A — Protect the body against diseases and help it work properly
Needed only in small amounts, vitamins and minerals keep the eyes, bones, teeth, skin and immune system healthy, and their lack causes deficiency diseases.
Q23. medium
Which foods are rich in vitamin A?
Answer: A — Carrot, papaya, mango, milk and green leafy vegetables
Orange and yellow fruits and vegetables, dark green leaves, milk, butter, eggs and fish liver oil are all good sources of vitamin A.
Q25. medium
Which foods are the best sources of vitamin C?
Answer: A — Amla, guava, orange, lemon and tomato
Citrus fruits, amla (Indian gooseberry), guava, tomato and green chillies are rich in vitamin C. It is destroyed by heat, so these are best eaten raw.
Q27. medium
Our body can make vitamin D when the skin is exposed to:
Answer: A — Sunlight
Ultraviolet rays in sunlight enable the skin to make vitamin D. This is why some morning sunshine each day is good for health, especially for children.
Q29. medium
Which mineral is essential for strong BONES and TEETH?
Answer: A — Calcium
Calcium builds and maintains bones and teeth. Milk, cheese, curd, ragi, green leafy vegetables and sesame seeds are rich sources.
Q31. medium
Which mineral is needed to make haemoglobin in the blood?
Answer: A — Iron
Haemoglobin, the red pigment that carries oxygen, contains iron. Green leafy vegetables, jaggery, dates, liver and pulses supply iron.
Q33. medium
Which mineral prevents GOITRE, a swelling of the neck?
Answer: A — Iodine
Iodine is needed by the thyroid gland. Its deficiency causes goitre and, in children, mental and physical retardation - which is why iodised salt is recommended.
Q35. medium
Dietary fibre, also called ROUGHAGE, is important because it:
Answer: A — Helps the body get rid of undigested food and prevents constipation
Roughage provides no nutrients but adds bulk to food, helping it move through the intestines and preventing constipation.
Q37. medium
Water is essential in our diet because it:
Answer: A — Helps absorb nutrients, removes wastes and controls body temperature
Water dissolves nutrients so the body can absorb them, carries away wastes in urine and sweat, and cools the body when sweat evaporates.
Q39. medium
A diet that contains all the nutrients in the right amounts is called:
Answer: A — A balanced diet
A balanced diet supplies carbohydrates, proteins, fats, vitamins, minerals, water and roughage in the proportions the body needs, along with enough variety.
Q41. medium
Diseases caused by the lack of a nutrient over a long period are called:
Answer: A — Deficiency diseases
Scurvy, rickets, anaemia, goitre, beriberi and night blindness are deficiency diseases. They are cured or prevented by supplying the missing nutrient.
Q43. medium
Why should vegetables NOT be washed AFTER cutting?
Answer: A — Water-soluble vitamins and minerals get washed away from the cut surfaces
Vitamin C and B vitamins dissolve in water. Once the vegetable is cut, these nutrients leach out from the exposed surfaces, so wash first and cut afterwards.
Q45. medium
Milk is called a nearly complete food because it contains:
Answer: A — Proteins, fats, carbohydrates, calcium and vitamins - almost all nutrients except iron and vitamin C
Milk supplies almost every nutrient in usable form, which is why it is ideal for infants. It is low in iron and vitamin C, so other foods are still needed.
Q47. medium
Which of these gives us food from animals?
Answer: A — Milk, eggs, honey, fish and meat
Animal products include milk and its products, eggs, honey, fish, chicken and meat. They are especially rich in protein.
Q49. medium
Growing children and pregnant women need extra:
Answer: A — Proteins, calcium, iron and vitamins
Rapid growth and the development of a baby demand extra body-building and protective nutrients, especially protein, calcium, iron and vitamins.
Q51. medium
Which food would you recommend to a person suffering from anaemia?
Answer: A — Green leafy vegetables, jaggery, dates and pulses (iron-rich foods)
Anaemia results from iron deficiency, so iron-rich foods are needed. Taking vitamin C along with them (a lemon squeeze) helps the body absorb the iron better.
Q53. medium
The main vitamins are grouped as:
Answer: A — A, B-complex, C, D, E and K
Vitamins A, D, E and K are fat-soluble, while B-complex and C are water-soluble and must be supplied regularly since the body cannot store them well.
Q55. medium
Which of these meals is the MOST balanced?
Answer: A — Chapati, dal, vegetable, curd and a fruit
This meal supplies carbohydrates from the chapati, protein from the dal and curd, vitamins and minerals from the vegetable and fruit, plus roughage and water.
Q57. medium
Which nutrient does NOT provide energy?
Answer: A — Vitamins
Vitamins and minerals regulate body processes but supply no energy. Carbohydrates, fats and, if needed, proteins are the energy-yielding nutrients.
Q59. medium
Which part of the plant do we eat when we eat GINGER?
Answer: A — An underground stem (rhizome)
Ginger and turmeric are rhizomes - horizontal underground stems that store food. Like the potato, they bear buds, which true roots never do.
Q5. hard
Animals that feed on dead and decaying animals are called:
Answer: A — Scavengers
Vultures, hyenas and crows are scavengers. By clearing away dead bodies they help keep the environment clean and prevent the spread of disease.
Q7. hard
A potato is which part of the plant?
Answer: A — A modified underground stem
The potato is a tuber - a swollen underground stem that stores food. Its 'eyes' are buds, which roots never have.
Q9. hard
Sprouted seeds are considered very nutritious because sprouting:
Answer: A — Increases the vitamin content and makes the seeds easier to digest
When seeds germinate, stored food is converted into simpler forms and vitamins (especially vitamin C) increase, so sprouts are both more nutritious and easier to digest.
Q12. hard
The two main types of carbohydrates in our food are:
Answer: A — Starch and sugars
Starch is found in rice, wheat, potato and maize; sugars are found in fruits, honey, sugarcane and milk. Both are digested to glucose.
Q14. hard
The test for PROTEIN uses copper sulphate and caustic soda, and a positive result shows:
Answer: A — A violet colour
Add a little water, then 2 drops of copper sulphate and 10 drops of caustic soda solution. A violet colour means protein is present.
Q16. hard
Nutrients that help in the GROWTH and REPAIR of the body are:
Answer: A — Proteins
Proteins are called body-building foods. They build muscles, skin, hair, blood and enzymes, and repair worn-out or injured tissues.
Q18. hard
Fats are important because they:
Answer: A — Give more energy than the same amount of carbohydrates and store energy for later use
Gram for gram, fats give roughly twice the energy of carbohydrates. The body stores excess fat under the skin, which also insulates against cold.
Q20. hard
Foods rich in carbohydrates and fats are together called:
Answer: A — Energy-giving foods
Carbohydrates and fats are the fuel of the body. Proteins are body-building foods, and vitamins and minerals are protective foods.
Q22. hard
Which vitamin is needed for good EYESIGHT?
Answer: A — Vitamin A
Vitamin A keeps the eyes and skin healthy. Its deficiency causes night blindness and, in severe cases, total loss of vision.
Q24. hard
The deficiency of vitamin C causes:
Answer: A — Scurvy - bleeding gums and slow healing of wounds
Vitamin C is needed for healthy gums, skin and blood vessels. Its lack causes scurvy, with swollen bleeding gums, loose teeth and poor wound healing.
Q26. hard
Vitamin D is important because it:
Answer: A — Helps the body absorb calcium and phosphorus for strong bones and teeth
Without vitamin D, calcium cannot be absorbed properly. Its deficiency causes rickets in children (bent, weak bones) and bone weakness in adults.
Q28. hard
Deficiency of vitamin B1 (thiamine) causes:
Answer: A — Beriberi - weak muscles and very little energy
Beriberi causes muscle weakness, nerve damage and extreme tiredness. Whole grains, pulses, meat and nuts supply vitamin B1.
Q30. hard
Deficiency of calcium and vitamin D leads to:
Answer: A — Rickets in children and weak, brittle bones in adults
Rickets makes children's bones soft, so their legs bow outwards. In adults, the same deficiency causes bone pain and easy fractures.
Q32. hard
Deficiency of iron causes:
Answer: A — Anaemia - weakness, tiredness and pale skin
With too little iron, the blood cannot carry enough oxygen. The person feels weak and tired and looks pale - a very common deficiency, especially among women and children.
Q34. hard
Iodised salt is recommended because it:
Answer: A — Supplies iodine and prevents goitre and related disorders
Many Indian soils lack iodine, so food grown there is deficient. Adding iodine to common salt is a simple, cheap way of reaching everyone.
Q36. hard
Which of these is the main source of roughage?
Answer: A — Whole grains, pulses, fresh fruits and vegetables
Roughage is mainly plant cellulose. Whole wheat, unpolished rice, pulses, fruits with skin and leafy vegetables all supply plenty of it.
Q38. hard
Besides drinking water, we also get water from:
Answer: A — Fruits, vegetables and other foods we eat
Most foods contain water - cucumber, watermelon and tomato are almost entirely water. The body also produces a little water during respiration.
Q40. hard
A balanced diet does NOT have to be expensive because:
Answer: A — Cheap local foods like pulses, seasonal vegetables, millets and sprouts are highly nutritious
Ragi, bajra, seasonal greens, pulses, groundnuts, jaggery and sprouted grams are inexpensive yet rich in proteins, minerals and vitamins.
Q42. hard
A serious protein deficiency in children causes:
Answer: A — Stunted growth, swelling of the face, and thin, weak limbs
Severe protein deficiency stops normal growth. The child becomes weak, the skin and hair change, and the body may swell with retained fluid.
Q44. hard
Which cooking practice destroys the MOST vitamins?
Answer: A — Overcooking and throwing away the water in which vegetables were boiled
Prolonged heating destroys vitamin C and B vitamins, and discarding the cooking water throws away the minerals that dissolved into it. Steaming or using the water in soup preserves them.
Q46. hard
Honey is produced by bees from:
Answer: A — The nectar of flowers
Bees collect nectar, store it in their honey sacs and process it in the hive, where it thickens into honey - a food rich in natural sugars.
Q48. hard
Why do people doing heavy physical work need MORE food than office workers?
Answer: A — Physical work uses much more energy, so more energy-giving food is needed
Energy needs depend on activity, age, sex and body size. A labourer or athlete burns far more energy than someone sitting at a desk, so needs a larger intake.
Q50. hard
Eating too much fat and sugar over a long time can cause:
Answer: A — Obesity, along with a higher risk of diabetes and heart disease
Excess energy is stored as fat. Obesity strains the heart and joints and increases the risk of diabetes and high blood pressure, so moderation matters.
Q52. hard
Which statement about vitamins is CORRECT?
Answer: A — They are needed in very small amounts but their absence causes serious diseases
Vitamins are micronutrients - a few milligrams a day is enough - yet the lack of even one causes a specific deficiency disease.
Q54. hard
Why must water-soluble vitamins like C and B be taken every day?
Answer: A — The body cannot store them - the excess is passed out in urine
Fat-soluble vitamins can be stored in the liver and fatty tissue, but water-soluble ones are excreted, so a regular daily supply from food is necessary.
Q56. hard
Germinating pulses before eating them is a good practice because it:
Answer: A — Increases vitamin content and makes them easier to digest, at almost no cost
Sprouting boosts vitamin C and B vitamins and breaks down substances that hinder digestion. It is a cheap way to improve the nutrition of a simple meal.
Q58. hard
Which overall statement about food is CORRECT?
Answer: A — A balanced diet supplying all nutrients in the right amounts is essential for growth, energy and protection against disease
This sums up the topic: carbohydrates and fats give energy, proteins build and repair, vitamins and minerals protect, roughage aids digestion and water carries it all - and no single food supplies everything.
Q60. hard
Why is it better to eat whole wheat flour (atta) than highly refined flour (maida)?
Answer: A — Whole wheat keeps the bran, so it supplies more roughage, vitamins and minerals
Refining removes the outer bran and the germ, and with them most of the fibre, B vitamins and minerals. Whole wheat retains them, aiding digestion and overall nutrition.